Metalloporphyrin as a Biomimetic Catalyst for the Catalytic Oxidative Degradation of Lignin to Produce Aromatic Monomers was written by Xie, Jinfeng;Ma, Guanfeng;Ouyang, Xinping;Zhao, Lisha;Qiu, Xueqing. And the article was included in Waste and Biomass Valorization in 2020.Electric Literature of C5H5NO This article mentions the following:
Lignin, an abundant biomass waste, was degraded under microwave irradiation with H2O2 as the oxidant and metalloporphyrin as the catalyst. The effect of substituent group (4-methylphenyl, 4-methoxyphenyl, 4-bromophenyl and 4-carboxyphenyl) at the meso-benzene ring of metalloporphyrin, central metal ion (Co, Mn, Ni and Fe) and axial ligand (chlorine, p-hydroxypyridine, p-pyridinecarboxaldehyde) on the degradation of lignin was investigated. The electron-withdrawing group not only reduces the electron cloud d. on the porphyrin ring, but also promotes the formation of higher active intermediate [(Porp)MeIV=O]+·. Therefore, the presence of stronger electron-withdrawing substituents makes the metalloporphyrins more efficient in lignin degradation Compared to Co porphyrin, there are less amount of [(Porp)MeIV=O]+· formed when Mn, Fe or Ni porphyrin was used as the catalyst for degrading lignin. Consequently, Co porphyrin contributed to a higher YAM (the yield of aromatic monomers). The strong nucleophilicity and the low steric hindrance of axial ligand was advantageous for the stability of metalloporphyrins, which is favorable for improving the catalytic activity to the degradation of lignin. It is found that the YAM increases 20.1% from 5.6% by using CoTBrPPCl as the reaction catalyst under the optimized conditions. In the experiment, the researchers used many compounds, for example, Pyridin-4-ol (cas: 626-64-2Electric Literature of C5H5NO).
Pyridin-4-ol (cas: 626-64-2) belongs to pyridine derivatives. Pyridine’s the lone pair does not contribute to the aromatic system but importantly influences the chemical properties of pyridine, as it easily supports bond formation via an electrophilic attack. Pyridine derivatives are also useful as small-molecule α-helix mimetics that inhibit protein-protein interactions, as well as functionally selective GABA ligands.Electric Literature of C5H5NO